This invention relates generally to complex interconnected electronics systems, such as advanced avionics systems in military aircraft, and, more particularly, to problems inherent in maintaining and testing such systems in their normal operational environment. Modern avionics systems make use of high-density electronic packaging and design techniques that greatly increase the functionality of the systems, but have an adverse impact on maintainability and producibility. The adverse impact arises largely because of an increased difficulty associated with detecting and identifying device and interconnect failures as they occur in the system. Many avionics systems perform highly critical functions that require fault-tolerant system designs, with the ability to detect and identify loss of function while in flight, and to reconfigure into backup, and possibly degraded, modes of operation. Such systems therefore require an "embedded" test capability, which has not been provided by traditional test techniques.
It will be appreciated from the foregoing that modern integrated avionics systems need the support of a diagnostic and test capability that improves the maintainability and producibility of the systems, and also provides embedded testing during flight conditions. The present invention addresses these problems from several distinct perspectives.